A three-way catalyst is known as an exhaust gas purifying catalyst installed in a vehicle and the like to oxidize or reduce harmful gas (hydrocarbon (HC), carbon monoxide (CO), nitrogen oxide (NOx)) contained in exhaust gas. Due to the recent increase in consciousness of environmental issues, regulations on exhaust gas emitted from a vehicle and the like have been further tightened. In response to such regulations, advances are being made in the improvement of three-way catalysts.
For example, a conventionally disclosed three-way catalyst contains catalyst powder that contains: a catalytic active species enclosure material in which catalytic active species containing noble metal particles supported on a metal oxide are covered with a high heat resistant oxide; and a promoter enclosure material in which promoter component particles are covered with a high heat resistant oxide (for example, refer to Patent Literature 1). In the catalyst powder, since the promoter component particles are covered with the heat resistant oxide, an aggregation of the promoter component particles and a decrease in specific surface area are suppressed. Accordingly, high durability can be exerted.